1. Technical Field
The inventive concept relates to a nonvolatile memory device, and more particularly, to a nonvolatile memory device performing a programming operation according to incremental step pulse programming (ISPP).
2. Discussion of the Related Art
Semiconductor memory devices (hereafter, “memory devices”) include volatile memory devices and non-volatile memory devices. Volatile memory devices are generally characterized by fast data access and write speeds, but lose stored data in the absence of applied power. In contrast, non-volatile memory devices generally provide slower data access and write speeds but retain stored data in the absence of applied power. Examples of nonvolatile memory devices include phase-change random access memory (PRAM), mask read-only memory (MROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and flash memory device.
Recently, flash memory devices have widely employed ISPP to program a memory cell by increasing, step-by-step, a voltage applied to a word line of the memory cell. According to a method of programming a memory cell by using Fowler Nordheim (FN) tunneling, the size of a write buffer is relatively large, while the amount of data to be read by using a sense amplifier is relatively small.
Accordingly, when the verification of the memory cell is performed, a relatively large of time is needed to update the write buffer with data that is read by the sense amplifier. Also, since data read time and write buffer update time are occur separately, the overall programming time is prolonged due to the read and update time when the ISPP is performed.